Based on preliminary data, the procedure used to purify myelinated axons from bovine intradural root and rabbit sciatic nerve will be refined to simultaneously yield myelin, axolemma-enriched and neurofilament fractions. Schwann cell membrane will be isolated from cultured rat sciatic nerve Schwann cell preparations and its properties will be compared to that of the other cell fractions. The enzymatic profile of all cellular fractions will be determined including positive and negative marker enzymes. The molecular weight profile of the fractions will also be determined by slab gel electrophoresis. Particular emphasis will be placed on demonstrating the cellular origin of the isolated fractions. PNS axolemma will be specifically labelled with locally injected radioactive precursors. This membrane will also be characterized with immunological markers such as tetanus toxin binding to the nerve in situ as well as in the isolated membrane fractions. Myelin and myelin-related fractions will be established using a radioimmunoassay for myelin basic protein and standard electron microscopic techniques. Finally the exact composition of the cellular fractions will be determined and compared.